Wafer processing apparatus and wafer processing method using the same

ABSTRACT

A wafer processing apparatus and a wafer processing method using the same are provided. A grinding wheel may include a wheel body having a plurality of wheel blades to remove a backside of a wafer, each of the plurality of wheel blades in an annular array with respect to each other and configured to move individually. A method of processing a wafer may include preparing a wafer for a backside processing, a first processing the backside of the wafer using a first wheel blade or a second wheel blade, and a second processing the backside of the wafer using only the second wheel blade.

A claim of priority is made under 35 U.S.C. § 119 to Korean Patent Application 2005-71481 filed on Aug. 4, 2005, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Example embodiments of the present invention relate to an apparatus and a semiconductor manufacturing method. More particularly, example embodiments of the present invention relate to a grinding wheel, wafer processing apparatus for processing a backside of a wafer and a method of processing a wafer using the same.

2. Description of Related Art

A wafer, which may be used to from integrated circuit (IC) devices thereon, is subjected to a plurality of manufacturing processes, for example, diffusion, photolithography, etching, ion implantation, and so on. After the manufacturing processes, an electrical die sorting (EDS) process to test electrical characteristics and operation states of IC devices formed on a wafer may be performed to determine whether or not the IC devices are properly functional. IC devices determined as properly functional after an EDS process may be cut into individual chips and subjected to an assembly process and a packaging process.

To prevent and/or reduce a wafer and its surface from being damaged during manufacturing and test processes, the wafer should have a desired thickness. However, to achieve miniaturization and higher integration of IC devices, it may be advantageous to use a thinner wafer. Therefore, although a wafer may have a certain thickness during manufacturing and test processes, after the completion of the test process, a thickness of the wafer may be reduced by processing (for example, grinding) a backside (a surface opposite an active side) of the wafer using a wafer processing apparatus having a single grinding wheel, prior to cutting the wafer into individual IC chips for assembly and packaging. For example, a thickness of a wafer is about 750 μm during manufacturing and test processes, and after the test process, grind and reduced to about 470 μm.

IC chips, which are utilized in state-of-the-art electronic devices, may be smaller in size but capable of high performance. Therefore, requirements placed on the IC chips have become more severe. For example, an IC chip used in a liquid crystal display (LCD) device or a smart card may be required to have a thickness of about 150 μm and a surface roughness of not more than 10 nm. However, conventional wafer processing apparatus employing a conventional grinding wheel may not be able to perform desired grinding.

While it is possible to produce a thinner IC chip with a surface roughness of less than 10 nm, because the IC chip may be grounded down from about 750 μm to about 150 μm using a grinding wheel, it may be time-consuming and/or less productive.

SUMMARY OF THE INVENTION

Example embodiments of the present invention may provide a wafer processing apparatus and a method of processing a wafer using the same.

In an example embodiment of the present invention, a grinding wheel may include a wheel body having a plurality of wheel blades to remove a backside of a wafer, each of the plurality of wheel blades in an annular array with respect to each other and configured to move individually.

In an example embodiment, a wafer processing apparatus may include a grinding wheel including a wheel body having a plurality of wheel blades to remove a backside of a wafer, each of the plurality of wheel blades in an annular array with respect to each other and configured to move individually, a processing head configured to detachably hold the wheel body, and a wafer chuck configured to hold the wafer during removal of the backside of the wafer.

In an example embodiment of the present invention, a method of processing a wafer may include preparing a wafer for a backside processing, primarily processing the backside of the wafer using first and second wheel blades, and secondarily processing the backside of the wafer using only the second wheel blade.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the present invention will be apparent from the detailed description of example embodiments of the present invention thereof and illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating example embodiments of the present invention.

FIG. 1 is a side view illustrating a wafer processing apparatus according to an example embodiment of the present invention.

FIG. 2 is a plan view illustrating a processing head shown in FIG. 1, viewed in direction A.

FIG. 3 is a cross-sectional view of the processing apparatus illustrated in FIG. 1 taken along line I-I′.

FIG. 4 is a cross-sectional view of a grinding wheel illustrated in FIG. 3, when a second wheel blade is lowered by a desired distance.

FIG. 5 is a bottom view of the grinding wheel illustrated in FIG. 3, viewed in direction B.

FIG. 6 is a bottom view of a grinding wheel according to another example embodiment of the present invention.

FIG. 7 is a bottom view of a grinding wheel according to another example embodiment of the present invention.

FIG. 8 is a cross-sectional view of a wheel moving unit according to an example embodiment of the present invention.

FIG. 9 is a cross-sectional view of a second wheel blade lowered by a desired distance using the wheel moving unit illustrated in FIG. 8.

FIG. 10 is a flowchart of a wafer processing method according to an example embodiment of the present invention.

FIG. 11 is a flowchart of a wafer processing method according to another example embodiment the present invention.

FIG. 12 is a flowchart of a wafer processing method according to another example embodiment the present invention.

DETAILED DESCRPTION OF EXAMPLE EMBODIMENTS OF THE PRESENT INVENTION

It will be understood that when an element or layer is referred to as being “on”, “connected to” or “coupled to” another element or layer, it may be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Example embodiments of the present invention are described herein with reference to cross-section illustrations that may be schematic illustrations of idealized embodiments (and intermediate structures) of the present invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, the example embodiments of the present invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the invention.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Referring to FIGS. 1 to 5, a wafer processing apparatus 100 to process, for example, grind and polish a backside of a wafer 90 according to an example embodiment of the present invention may include a wafer chuck 150 to seat the wafer 90. The wafer 90 may be loaded with a protection tape 95, for example, a UV tape, adhered to a surface on which devices are formed, and an opposite side thereof is directed away from the wafer chuck 150. The wafer chuck 150 may fix the wafer 90 using vacuum suction by other well known methods. In addition, the wafer chuck 150 may be rotatably installed to rotate at a desired rpm when a wafer 90 is grounded.

A processing head 120 may be disposed over the wafer chuck 150 to process a backside of the wafer 90. The processing head 120 may be installed to vertically move up and down by a desired distance. Therefore, after the wafer 90 is seated on the wafer chuck 150, the processing head 120 may be lowered to the wafer chuck 150 by a desired distance to process the wafer 90.

The processing head 120 may include a grinding wheel 127 having a plurality of wheel blades 125, 126 (FIG. 5) at its lower portion thereof to process the wafer 90, wheel moving units 130 and 230 to raise/lower at least one of the wheel blades, a wheel clamp 123 to clamp the grinding wheel 127 at an upper portion thereof to rotate the grinding wheel 127, and a head motor 121 to rotate the wheel clamp 123 at a desired rpm.

The grinding wheel 127 may include a circular disc-shaped wheel body 124, and the wheel blades 125, 126 disposed at a lower portion thereof. The wheel body 124 may be detachably installed at a lower portion of the wheel clamp 123. Therefore, when a desired number of wafers have been ground, a user may separate the wheel body 124 from the wheel clamp 123 to replace the grinding wheel 127. The wheel blades 125, 126 may be in contact with the backside of the wafer 90 to directly process the wafer 90. Therefore, the wheel blades 125, 126 may be formed and disposed in various shapes.

In an example embodiment of the present invention, a wheel blade may be formed and disposed as shown in FIG. 5. Specifically, the wheel blades may include a first annular wheel blade 125 disposed at an inner circumference of the wheel body 124, and a second annular wheel blade 126 disposed at an inner circumference of the first wheel blade 125. The first and second wheel blades 125 and 126 may include diamond materials having different grit sizes and annularly disposed thereof. The first and second wheel blades 125 and 126 are not limited to diamond materials. The first wheel blade 125 may have a grit size of 2000 mesh, and the second wheel blade 126 may have a grit size of 3000 mesh. In addition, the first and second wheel blades 125 and 126 may be made of different materials from each other. For example, the first wheel blade 125 may include diamond grits sintered with resin, e.g., a diamond material, and the second wheel blade 126 may be made of polyethylene fibers compressed with polymer, e.g., an unwoven material. Accordingly, the first wheel blade 125 may grind the backside of the wafer 90 while the second wheel blade 126 polishes the wafer 90.

In another example embodiment of the present invention, wheel blades may be formed and disposed as shown in FIG. 6. That is, the wheel blades may include a first annular wheel blade 225 disposed at an inner circumference of a wheel body 224, a second annular wheel blade 226 disposed at inner circumference of the first wheel blade 225, and a third annular wheel blade 227 disposed at an inner circumference of a second wheel blade 226. The first, second and third wheel blades 225, 226 and 227 may include diamond materials having different grit sizes and annularly disposed thereof. The first wheel blade 225 may have a grit size of 2000 mesh, the second wheel blade 226 may have a grit size of 2500 mesh, and the third wheel blade 227 may have a grit size of 3000 mesh. In addition, the first, second and third wheel blades 225, 226 and 227 may include different materials. For example, the first and second wheel blades 225 and 226 may include diamond materials having different grit sizes, and the third wheel blade 227 may include an unwoven material of polyethylene fibers compressed with polymer. Accordingly, the first and second wheel blades 225 and 226 may grind the backside of the wafer 90 while the third wheel blade 227 polishes the wafer 90.

In still another example embodiment of the present invention, wheel blades may be formed and disposed as shown in FIG. 7. That is, the wheel blades may include a first annular wheel blade 325 disposed at an inner circumference of a wheel body 124, and a second circular wheel blade 329 disposed at an inner circumference of the first wheel blade 325. The first and second wheel blades 325 and 329 may be made of different materials. For example, the first wheel blade 325 may include diamond grits sintered with resin, e.g., a diamond material, and the second wheel blade 329 may be made of polyethylene fibers compressed with polymer, e.g., an unwoven material. Accordingly, the first wheel blade 325 may grind the backside of the wafer 90 while the second wheel blade 329 polishes the wafer 90.

The wheel moving units 130 and 230 are configured to raise/lower at least one of the wheel blades of the grinding wheel 127. For example, the wheel moving units 130 and 230 may be employed as a ball screw type, a cylinder type, a linear motor type, or the like.

With reference to FIGS. 2 to 5, the wheel moving units 130 and 230 may include connecting shafts 139 and 239 connected to upper portions of the wheel blades 125 and 126; bearings 137 and 237 mounted on one end of the connecting shafts 139 and 239; cams 138 and 238 contacting the bearings 137 and 237 to move the connecting shafts 139 and 239 to a desired distance in a vertical direction; rotating shafts 134 and 234 connected to the cams 138 and 238; rotary motors 132 and 232 to rotate the rotating shafts 134 and 234 to reciprocate the cams 138 and 238 and simultaneously move the rotating shafts 134 and 234 by a desired distance; and resilient members 131 and 231 to return the connecting shafts 139 and 239 to their original positions. A plurality of wheel moving units 130 and 230 may be disposed along the perimeter of a wheel clamp 123 by a desired angular interval. A desired size of through-holes 122 and 135 may be formed in a wheel body 124 and the wheel clamp 123, so that the connecting shafts 139 and 239 may pass therethrough, respectively. In addition, an installation space 133 may be provided on the connecting shafts 139 and 239 and in communication with the through-holes 135 formed at the wheel clamp 123 for installation of the cams 138 and 238 or the connecting shafts 134 and 234.

Specifically, the bearings 137 and 237 may be formed in a spherical shape. The connecting shafts 139 and 239 may have concave parts at their upper ends so that the spherical-shaped bearings 137 and 237 can roll without separating from the upper ends of the connecting shafts 139 and 239 to the exterior. In addition, the cams 138 and 238 may be sloped at their lower surfaces to push the bearings in contact with the cams 138 and 238 down when the cams 138 and 238 move inward by the rotation of the rotating shafts 134 and 234. For example, the cams 138 and 238 may have a trapezoidal shape. The rotating shafts 134 and 234 may be cylindrical, have a desired length, and may be provided with one end connected to the cams 138 and 238 and the other end passing through or inserted into the rotary motors 132 and 232. The rotating shafts 134 and 234 may be threaded, and the rotary motors 132 and 232 may include rotors having desired size nuts (not shown) through which the rotating shafts 134 and 234 are inserted therein. The nuts provided at the rotors may have threads corresponding to the threads of the rotating shafts 134 and 234. Therefore, when the rotary motors 132 and 232 are rotated clockwise or counterclockwise, the rotating shafts 134 and 234 may be reciprocated forward and backward by the threads.

In addition, the resilient members 131 and 231 serve to return the connecting shafts 139 and 239 moved by the cams 138 and 238 to their original positions, which may be coil springs disposed between a desired size of hooking projections 140 and 240 projecting from side surfaces of the connecting shafts 139 and 239. Therefore, when the cams 138 and 238 do not push the connecting shafts 139 and 239 down, the lowered connecting shafts 139 and 239 pushed by the cams 138 and 238 of the wheel moving units 130 and 230 can return to their original positions by the resilient force of the resilient members 131 and 231 supported between the projections 128 and 140 and 228 and 240. The hooking projections 140 and 240, the support projections 128 and 228, and the resilient members 131 and 231 may be installed in the through-hole 122.

The wheel moving units 130 and 230 may further include distance detectors 136 and 236 disposed at a side of the rotary motors 132 and 232, respectively, to detect a moving distance of the cams 138 and 238. The wheel blades 125 and 126 may be lowered in proportion to the moving distance of the cams 138 and 238, and a central controller (not shown) to may be used to control the wafer processing apparatus 100 and to control the rotation of the rotary motors 132 and 232 on the basis of data transmitted from the distance detectors 136 and 236 to control the moving distance of the cams 138 and 238 and the lowering distance of the wheel blades 125 and 126. The distance detectors 136 and 236 may be an encoder to generate a desired signal according to a distance to be moved by the cams 138 and 238 and the rotating shafts 134 and 234.

FIGS. 8 and 9 show wheel moving units 130′ and 230′ accordingly to other example embodiments of the present invention. The wheel moving units 130′ and 230′ may include piston rods 139′ and 239′ disposed on wheel blades 125 and 126, and cylinders 132′ and 232′ connected to the piston rods 139′ and 239′ configured to raise/lower the piston rods 139′ and 239′. The cylinder 132′ and 232′ may be a hydraulic or air cylinder.

Hereinafter, a method of processing a wafer using a wafer processing apparatus in accordance with example embodiments of the present invention will be described in detail.

FIG. 10 is a flowchart of a wafer processing method according to an example embodiment of the present invention; FIG. 11 is a flowchart of a wafer processing method according to another example embodiment the present invention; and FIG. 12 is a flowchart of a wafer processing method according to still another example embodiment the present invention.

A method of processing a wafer using a wafer processing apparatus in accordance with an example embodiment of the present invention will be described with reference to FIG. 5-7, and 10.

A wafer 90 to be ground may be transferred by a wafer transfer robot (not shown) onto a wafer chuck 150 (S11).

After the wafer 90 is loaded onto the wafer chuck 150, the wafer chuck 150 may fix the loaded wafer 90 onto an upper surface thereof using a vacuum suction method or another well known method.

After the wafer 90 is fixed, a processing head 120 may be lowered to the wafer chuck 150 by a desired distance to primarily process the wafer 90 using a plurality of wheel blades arranged at a lower portion thereof (S13). A wheel clamp 123 arranged at the processing head 120 and a grinding wheel 127 clamped by the wheel clamp 123 may be rotated by a head motor 121 in a first direction, and the wafer chuck 150 may be rotated in a second direction, e.g., opposite to the rotation of the grinding wheel 127. The plurality of wheel blades may include diamond materials having different grit sizes and disposed in an annular array on the wheel blades. For example, a first wheel blade may have a grit size of 2000 mesh and a second wheel blade may have a grit size of 3000 mesh.

After the primary processing, the processing head 120 may be raised above the wafer chuck 150 by a desired height and then at least one of the plurality of wheel blades may be lowered by a desired distance (S15). The lowered wheel blades may have the smallest grit size among the plurality of wheel blades.

After the at least one of the plurality of wheel blades is lowered by the desired distance, the processing head 120 may be lowered again onto the upper surface of the wafer chuck 150, and secondarily process the wafer 90 using only the at least one of the lowered wheel blades (S17).

After the primary and secondary processing, the wafer transfer robot may unload the wafer 90, thereby completing the wafer processing (S19).

Hereinafter, another example embodiment of the present invention of a wafer processing method using a wafer processing apparatus in accordance with the present invention will be described with reference to FIGS. 5-7, and 11.

A wafer 90 to be ground is transferred by a wafer transfer robot onto a wafer chuck 150. After the wafer 90 is loaded onto the wafer chuck 150, the wafer chuck 150 may fix the loaded wafer 90 to an upper surface of the wafer chuck 150 using a vacuum suction method or another well known method (S21).

After the wafer 90 is fixed, a processing head 120 may lower a first wheel blade (or a first subset of the wheel blades) by a desired distance, the processing head 120 may be lowered towards the wafer chuck 150 until the first wheel blade contacts the wafer 90 and primarily processes the wafer 90 (S23). The first wheel blade may include diamond materials having a grit size of 2000 mesh.

After the primary processing, the processing head 120 may be raised above the wafer chuck 150 by a desired distance, the lowered first wheel blade may be raised, and a second wheel blade (or a second subset of the wheel blades) may be lowered by a desired distance (S25).

After the second wheel blade is lowered by the desired distance, the processing head 120 may be lowered again onto the upper surface of the wafer chuck 150 and secondarily process the wafer 90 using the second wheel blade (S27). The lowered second wheel blade may include diamond materials having a grit size of 3000 mesh.

After the wafer 90 is ground by the primary and secondary processing, the wafer transfer robot may unload the wafer 90 seated on the wafer chuck 150 to complete the wafer processing (S29).

Another example embodiment of the present invention of a wafer processing method using a wafer processing apparatus in accordance with the present invention will now be described with reference to FIGS. 5-7, and 12.

A wafer 90 to be ground may be transferred by a wafer transfer robot onto a wafer chuck 150 (S21). After the wafer 90 may be loaded onto the wafer chuck 150, the wafer chuck 150 may fix the loaded wafer 90 to an upper surface of the wafer chuck 150 using a vacuum suction method or another well known method.

After the wafer 90 is fixed, a processing head 120 may lower a first wheel blade (or a first subset of the wheel blades) by a desired distance, the processing head 120 may be lowered towards the wafer chuck 150 until the lowered first wheel blade contacts the wafer 90 and then primarily processes the wafer 90 using the lowered first wheel blades (S23). The lowered first wheel blade may include diamond materials having a grit size of 2000 mesh.

After the primary processing, the processing head 120 may be raised above the wafer chuck 150 by a desired distance, the first wheel blade may be raised, and a second wheel blade (or a first subset of the wheel blades) may be lowered by a desired distance (S25).

After the second wheel blade is lowered by the desired distance, the processing head 120 may be lowered again onto the upper surface of the wafer chuck 150 and secondarily polish the wafer 90 using the lowered second wheel blade (S28). The second wheel blade may include an unwoven material. The first wheel blade may primarily process a backside of the wafer 90, e.g., perform rough processing or grinding, and the second wheel blade may secondarily polish the backside of the wafer 90, e.g., performs fine polishing.

After the wafer 90 is ground by the primary processing and secondary polishing, the wafer transfer robot may unloads the wafer 90 to complete the wafer processing process (S29).

It should be appreciated that the first and second wheel blades disclosed above with respect to FIGS. 5-7, 10, 11, and 12, may include more than one blade. For example, the second blade may include more than one blade.

As should be also appreciated from the foregoing disclosure, a wafer processing apparatus and a wafer processing method using the same in accordance with example embodiments of the present invention may be capable of improving surface roughness of wafers by reducing a thickness of wafers by processing the wafer using a plurality of wheel blades having different grit sizes and/or different materials.

In addition, it may be possible to polish and process a wafer by performing a primary grinding process using wheel blades made of a diamond material and a secondary polish process using wheel blades made of an unwoven material. As a result, a time required to process the wafer may be reduced, and thus productivity may be increased.

While example embodiments of the present invention has been described in connection with example embodiments thereof, it is to be understood that the example embodiments of the present invention is not limited to the disclosed example embodiments but is intended to cover various modifications within the scope of the present invention. 

1. A grinding wheel comprising a wheel body having a plurality of wheel blades to remove a backside of a wafer, each of the plurality of wheel blades in an annular array with respect to each other and configured to move individually.
 2. The grinding wheel according to claim 1, wherein the plurality of wheel blades includes diamond materials.
 3. The grinding wheel according to claim 1, wherein each of the plurality wheel blades have different grit sizes.
 4. The grinding wheel according to claim 1, wherein the plurality of wheel blades are concentric with respect to each other.
 5. The grinding wheel according to claim 1, wherein the plurality of wheel blades includes a first wheel blade including diamond materials and a second wheel blade including nonwoven materials.
 6. The grinding wheel according to claim 5, wherein the second wheel blade is configured in an inner circumference of the first wheel blade.
 7. A wafer processing apparatus comprising: a grinding wheel including a wheel body having a plurality of wheel blades to remove a backside of a wafer, each of the plurality of wheel blades in an annular array with respect to each other and configured to move individually; a processing head configured to detachably hold the wheel body; and a wafer chuck configured to hold the wafer during removal of the backside of the wafer.
 8. The wafer processing apparatus according to claim 7, further comprising a wheel moving unit, including: a connecting shaft configured to engage at least one of the plurality of wheel blades; a bearing at one end of the connecting shaft; a cam contacting the bearing and configured to enable movement of the connecting shaft and to reciprocate in a vertical direction of the connecting shaft by a desired distance; a rotating shaft connected to the cam; and a rotary motor configured to rotate the rotating shaft, to reciprocate the cam and simultaneously reciprocate the rotating shaft by a desired distance.
 9. The wafer processing apparatus according to claim 8, wherein the wheel moving unit further includes a distance sensor disposed on the rotary motor configured to sense a moving distance of the cam.
 10. The wafer processing apparatus according to claim 8, wherein the wheel moving unit further includes a resilient member adapted to return the connecting shaft moved by the cam to an original position.
 11. The wafer processing apparatus according to claim 7, wherein the wheel moving unit includes: a piston rod configured to engage at least one of the plurality of wheel blades; and a cylinder connected to the piston rod and configured to move the piston rod by a desired distance.
 12. A method of processing a wafer, comprising: preparing a wafer for a backside processing; primarily processing the backside of the wafer using a first wheel blade or a second wheel blade; and secondarily processing the backside of the wafer using only the second wheel blade.
 13. The method according to claim 12, wherein the primarily processing and the secondarily processing each include grinding the wafer.
 14. The method according to claim 12, wherein the primarily processing uses only the first wheel blade.
 15. The method according to claim 14, wherein the primarily processing and the secondarily processing each include grinding the wafer.
 16. The method according to claim 14, wherein the primarily processing includes grinding the wafer and the secondarily processing includes polishing the wafer.
 17. The method according to claim 12, wherein the first wheel blade and the second wheel blade include diamond materials.
 18. The method according to claim 17, wherein the first wheel blade and the second wheel blade have different grit sizes.
 19. The method according to claim 17, wherein the second wheel blade has a grit size smaller than a grit size of the first wheel blade.
 20. The method according to claim 16, wherein the first wheel blade includes diamond materials and the second wheel blade includes unwoven materials. 